Airfield lighting is customarily used in the aviation industry to outline and make more visible various portions of an airport, such as runways and taxiways. Depending upon the size of an airport, airfield light fixtures may number in the hundreds or even thousands. As a result, airport operators often spend a great deal of time maintaining airfield lights for compliance with safety and various other requirements. Accordingly, airfield lights can contribute—often substantially—to the overall cost of airport maintenance.
Aviation regulatory agencies have certain minimum standards with respect to the visual characteristics of light provided by various airport runway, taxiway and threshold edge light fixtures, particularly the color of the light emitted by the fixtures. For example, runway edge lights are white in color, except on instrument-approach approved runways where yellow replaces white on the last 600 meters (2,000 feet) or half the runway length, whichever is less, to form a caution zone for landings. The lights marking the ends of the runway emit red light toward the runway to indicate the end of the runway to departing or arriving aircraft and emit green light outward from the runway end to indicate the threshold to landing aircraft. Taxiway lights are designed to emit blue light.
Light sources commonly used in airfield applications include incandescent, halogen, gas-arc and cold-cathode fluorescent types. The color of light emitted by the light source must usually be changed or “shifted” by use of unique optical filters in order to meet regulatory agency color requirements. Changing the color of the light emitted by light fixtures having these types of light sources to another color usually requires changing the optical filters, which can be costly, cumbersome and time-consuming.
More recently, light emitting diodes (LEDs) have become available for use as light sources in airfield lighting. LEDs are typically monochromatic-colored emitters or phosphor-converted white light emitters. Changing the color of light emitted by light fixtures having LEDs typically requires that the LEDs be replaced with ones having the desired colors, and may further require changing of an optical filter.
Regardless of the type of light source, a multitude of expensive spare parts are required to provide the spectrum of aviation colors required by regulatory agencies for the various types of light fixtures. Such a spare parts inventory can place a strain on an airport's maintenance budget as well as consuming valuable storage space. Accordingly, there is a need for a way to reduce the number of spare lighting fixtures that must be held in inventory by airport maintenance departments.